package com.yhxd.modular.news.controller;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.net.URLEncoder;
import java.util.HashMap;
import java.util.Map;

public class DownloadFileController extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)
             throws ServletException, IOException {
                 //获取下载的目标路劲
                 String downloadUrl="http://localhost:8082/file/upload/";
                 //得到要下载的文件名
                 String fileName = request.getParameter("filename");
                 fileName = new String(fileName.getBytes("iso8859-1"),"UTF-8");
                 //上传的文件都是保存在/WEB-INF/upload目录下的子目录当中
                 String fileSaveRootPath=downloadUrl;
                 //通过文件名找出文件的所在目录
                 String path = findFileSavePathByFileName(fileName,fileSaveRootPath);
                 //得到要下载的文件
                 File file = new File(path + "\\" + fileName);
                 //如果文件不存在
                 if(!file.exists()){
                         request.setAttribute("message", "您要下载的资源已被删除！！");
                         request.getRequestDispatcher("/message.jsp").forward(request, response);
                         return;
                     }
                 //处理文件名
                 String realname = fileName.substring(fileName.indexOf("_")+1);
                 //设置响应头，控制浏览器下载该文件
                 response.setHeader("content-disposition", "attachment;filename=" + URLEncoder.encode(realname, "UTF-8"));
                 //读取要下载的文件，保存到文件输入流
                 FileInputStream in = new FileInputStream(path + "\\" + fileName);
                 //创建输出流
                 OutputStream out = response.getOutputStream();
                 //创建缓冲区
                 byte buffer[] = new byte[1024];
                 int len = 0;
                 //循环将输入流中的内容读取到缓冲区当中
                 while((len=in.read(buffer))>0){
                         //输出缓冲区的内容到浏览器，实现文件下载
                         out.write(buffer, 0, len);
                     }
                 //关闭文件输入流
                 in.close();
                 //关闭输出流
                 out.close();
             }

             /**
      * @Method: findFileSavePathByFileName
      * @Description: 通过文件名和存储上传文件根目录找出要下载的文件的所在路径
      * @Anthor:孤傲苍狼
      * @param filename 要下载的文件名
      * @param saveRootPath 上传文件保存的根目录
      * @return 要下载的文件的存储目录
      */
             public String findFileSavePathByFileName(String filename,String saveRootPath){
                 int hashcode = filename.hashCode();
                 int dir1 = hashcode&0xf;  //0--15
                 int dir2 = (hashcode&0xf0)>>4;  //0-15
                 String dir = saveRootPath + "\\" + dir1 + "\\" + dir2;  //upload\2\3  upload\3\5
                 File file = new File(dir);
                 if(!file.exists()){
                         //创建目录
                         file.mkdirs();
                     }
                 return dir;
             }

             public void doPost(HttpServletRequest request, HttpServletResponse response)
             throws ServletException, IOException {
                 doGet(request, response);
             }
}
